Physicochemical and structural study of iodine loading in amorphous degradable starch microspheres

Iodine is a well-established antimicrobial agent, but its clinical use is limited by low chemical stability and adverse effects. This work investigates iodine loading into degradable starch microspheres (DSM), elucidating iodine–starch interactions, and structural changes after iodine uptake. Iodine complexation was achieved using a KI/I₂ system, yielding a characteristic purplish-red coloration within the DSM. Swelling and sedimentation analyses showed a slight reduction in DSM density after iodine absorption, without negative impact on hydration capacity. A UV–Vis spectrophotometric method targeting the triiodide band at 352 nm enabled robust quantification of iodine by leveraging equilibrium among iodine species. Sorption isotherms revealed cooperative binding behavior, with iodine uptake increasing nonlinearly in response to the external iodine concentration. Small- and wide-angle X-ray scattering (SWAXS) showed iodine-induced ordering across multiple length scales, including a reduction in the dynamic correlation length and the emergence of characteristic peaks associated with iodine–amylose complex. These results elucidate the physicochemical mechanisms governing iodine incorporation into DSM and highlight the structural consequences of loading, providing a framework for designing starch-based carriers for controlled iodine release.